Methodology

Formulas, assumptions, warning thresholds and calculation limits.

Formulas

Dew point uses a Magnus approximation. Absolute humidity is derived from saturation vapour pressure. Air replacement uses an ideal-mixing model: the replaced fraction is 1−e^−n·t.

Warning thresholds

Surface thresholds of 80%, 90% and 100% RH are screening indicators. They do not predict the growth of a specific mould species. EPA identifies moisture control as the key to mould control and advises keeping indoor RH below 60%, ideally 30–50% where possible.

Sources

• US EPA — Why and Where Mold Grows
• US EPA — Mold, Moisture and Your Home
• WHO — Dampness and Mould
• ASHRAE Standards and Guidelines

Limitations

The service does not check legal compliance or design a ventilation system. Real airflow requires measurement, while reverse draught, combustion fumes, leaks and major water damage need a professional.